What’s the Difference Between Canker Sores and Cold Sores?

The oral lesions caused by canker sores and cold sores may appear and feel similar, but they actually have different causes.

Canker sores occur only in the soft tissues of the mouth, such as on your gums or inside your cheeks. They can be caused by a variety of factors, including injury to the inside of your mouth and vitamin deficiencies.

Canker sores

Canker sores occur only on the inside of your mouth. They can be found in the following areas:

gums

inside your cheeks or lips

on or below your tongue

soft palate, which is the soft, muscular area found in the back area of the roof of your mouth

You may notice a burning or tingling feeling before canker sores appear.

Canker sores are typically round or oval in shape. They can appear to be white or yellow, and may have a red border.

Canker sores can also vary in size from small to large. Large canker sores, which can also be referred to as major canker sores, may be quite painful and take longer to heal.

Herpetiform canker sores, a less common type of canker sore, occur in clusters and are the size of pinpricks. This type of canker sore typically develops later in life.

Cold sores

The symptoms of a cold sore can depend on if you have a new infection with HSV or have had the virus for a while.

Those with a new infection may experience:

burning or tingling, followed by the development of painful sores on or around the lips, in the mouth, on the nose or other areas of the face

sore throat or pain when you swallow

fever

body aches and pains

headache

nausea

swollen lymph nodes

If you’ve had the virus for a long time, you may experience periodic outbreaks of cold sores. These outbreaks typically follow several phases, including:

warning signs in the area of the outbreak, which can include a burning, stinging, or itching sensation

appearance of cold sores, which are filled with fluid and are often painful

crusting over of the cold sores, which happens when the cold sores break open and form scabs

healing of cold sores, typically without a scar, in one to two weeks.

How do I tell the difference?

The location of the sore can often help you tell if it’s a canker sore or a cold sore. Canker sores only occur inside the mouth while cold sores often occur on the outside of the mouth around the area of the lips.

Most people are infected with HSV during childhood. After a new HSV infection, children under age 5 may have cold sores inside of their mouth that can sometimes be mistaken for canker sores.

Cold sores

Cold sores are caused by infection with specific strains of HSV. HSV-1 is the strain that most commonly causes cold sores. However, HSV-2, the strain that causes genital herpes, can also cause cold sores.

HSV is very contagious. The virus is most contagious when oozing cold sores are present, although it can be transmitted even if cold sores aren’t present.

HSV-1 can be spread through things such as sharing eating utensils or toothbrushes, or through kissing. Oral sex may spread HSV-2 to the mouth and lips, and may also spread HSV-1 to the genitals.

After you’ve contracted the infection, some factors may lead to the development of cold sores, including:

stress

fatigue

being sick with the flu or a cold

sunlight exposure

changes in hormones, such as during menstruation

irritation to the area where you have cold sores, which can be due to injury, dental work, or cosmetic surgery

While the exact cause of canker sores is uncertain, you can help prevent them by doing things such as protecting your mouth from injury, eating a healthy diet, and reducing stress.

Most canker sores will go away on their own in a week or two.

Cold sores are caused by HSV infection. Once you have the infection, you have the virus for your lifetime. Some people with HSV will never have cold sores while others will experience periodic outbreaks.

Cold sores should clear up on their own in a few weeks, although antiviral medications may speed healing. You should be particularly conscious to avoid skin-to-skin contact or the sharing of personal items when you have a cold sore, as this could spread the virus to others.

Medically reviewed by Cynthia Cobb, APRN on December 21, 2018 — Written by Jill Seladi-Schulman, PhD